When cranky old Carl Fredricksen a widower and former balloon salesman, lifts his house with a thousand helium-filled balloons and soars off on a long-anticipated quest, the last thing on his mind is a kid or a dog. So, that’s exactly what directors Pete Docter and Bob Peterson give him in Up, Pixar Animation Studio’s latest feature film.

“When Carl goes on his adventure, we give him a new family,” Peterson says. “A grandchild, essentially, and a dog. Because everyone has to have a dog.”

Carl and his stowaway, eight-year-old Russell, meet the Golden Retriever/Lab mix in a South American jungle. When the dog, tongue hanging out, tail wagging, jumps up on Carl, we hear, “Hi there. My name is Dug. My master made me this collar so that I may talk.” Dug suddenly whips his head to the left, says “Squirrel!” and freezes for a beat before turning back to Carl, who is not amused.

Three other dogs star alongside Dug in Up: Alpha, a Doberman, who leads the pack of hunting dogs; Beta, a Rottweiler; and Gamma, an English Bulldog. They are all caricatures, of course, but they act more like canines than cartoons.

“Dogs are so smart and emotional,” Peterson says. “They really do talk to you, but you still want to know what they’re thinking. It was our fantasy to put their thoughts on the screen and keep their natural dog behavior.”

Since having dogs lip-synching to human dialogue is hardly natural, the thought-translating collar gave Pixar the best of both worlds. “We could have a dog yelling while scratching his ear,” Peterson says. “And that dichotomy is funny.”

To help the artists and animators dig into dog and pack behavior, Pixar brought in behaviorist Ian Dunbar. “He gave us great knowledge about how dogs communicate and give signals,” Peterson says.

But the squirrel gag comes from Peterson’s own dogs; that is, from a game he plays with his German Shepherd and Cavalier King Charles Spaniel. “They’re sitting around, relaxed and panting,” he says. “I sit next to them and pant with them. And then I suddenly stop and look in another direction and they do, too. When I relax, they relax with me. Then we do it again. Dogs have great senses of humor.”

So, did Peterson’s Dug wag a smile out of cranky Carl? No spoilers, but we will say we wish a tail-wagging dog could adopt every grumpy old guy.